$\dfrac{9}{12} - \dfrac{1}{4} = {?}$
Answer: $ = {\dfrac{9 \times 1}{12 \times 1}} - {\dfrac{1 \times 3}{4 \times 3}} $ $ = {\dfrac{9}{12}} - {\dfrac{3}{12}} $ $ = \dfrac{{9} - {3}}{12} $ $ = \dfrac{6}{12}$